1. Field of the Invention
The present invention relates to a stroke identifying unit. The stroke identifying unit is capable of working in conjunction with an electronic fuel injection controller of a four-stroke engine.
2. Description of the Relevant Art
In the background art, an electronic fuel injection controller for a four-stroke engine works in conjunction with a stroke identifier in order to properly time fuel injections for individual cylinders of the engine. The stroke identifier, of the background art, identifies the strokes of the individual cylinders on the basis of a relationship between a phase of a crankshaft, detected by a crank sensor, and a phase of a camshaft, detected by a cam sensor.
In order to detect the phase of the camshaft, the cam sensor has to be disposed in a cylinder head of the engine. The cylinder head has to be enlarged in order to accommodate the cam sensor. The cost of the cam sensor and the enlargement of the cylinder head increase the overall cost of the engine. Moreover, when the engine is used to power a motorcycle, the enlarged cylinder head is undesirable, since the engine of a motorcycle is subject to a height limitation.
In a four-stroke engine, each cylinder undergoes four strokes, i.e., suction, compression, combustion and exhaust strokes, for every two rotations of the crankshaft. Therefore, simply detecting the phase of the crankshaft does not provide enough information to distinguish the suction stroke from the combustion stroke, or the compression stroke from the exhaust stroke.
The present invention utilizes the fact that pressures in intake pipes communicating with intake ports for each engine cylinder vary cyclically during every two rotations of the crankshaft. The present invention uses this fact to distinguish the intake stroke from the combustion stroke, and the compression stroke from the exhaust stroke, for the individual cylinders. When the cyclically varying pressures are analyzed, in conjunction with the phase of the crankshaft, the strokes of the individual cylinders can be accurately detected.
Accordingly, the present invention provides a stroke identifying unit, which can identify cylinder strokes, without detecting a phase of a camshaft.
Therefore, it is a primary object of the present invention to provide a stroke identifying unit which does not require enlargement of the cylinder head of the engine.
Further, it is an object of the present invention to invention to provide a stroke identifying unit which does not require the cost of a cam sensor.
These and other objects are fulfilled by providing a stroke identifying unit of a four-stroke engine comprising: a phase detector for detecting a phase of a crankshaft of the engine; a first intake pressure sensor for detecting an intake air pressure in a first intake pipe communicating with a first cylinder of the engine; and a stroke identifier for distinguishing strokes of the first cylinder based upon a relationship between the detected phase of the crankshaft and the detected intake pressure in the first intake pipe.
Further, these and other objects are fulfilled by providing a fuel injected engine comprising: an engine block; a crankshaft disposed in said engine block; an encoder attached to said crankshaft; a reader proximate said crankshaft for detecting said encoder and for generating a position signal in response to detecting said encoder; a plurality of cylinders in said engine block; a plurality of intake paths, each communicating with a respective one of said plurality of cylinders; a plurality of pressure sensors, each communicating with a respective one of said plurality of intake paths, and each generating a pressure signal representative of a pressure with the respective cylinder; a plurality of fuel injectors, each communicating with a respective one of said plurality of intake paths; and a control unit for receiving said position signal and said pressure signals, and for controlling an injection timing of said plurality of fuel injectors.
Moreover, these and other objects are fulfilled by providing a method of distinguishing a stroke of a cylinder of an engine comprising: providing a phase detector; providing a first intake pressure sensor; providing a stroke identifier; detecting a phase of a crankshaft of the engine; detecting an intake air pressure in a first intake pipe communicating with a first cylinder of the engine; and distinguishing strokes of the first cylinder based upon a relationship between the detected phase of the crankshaft and the detected intake pressure in the first intake pipe.
Other objects and further scope of applicability of the present invention will become apparent from the detailed description given hereinafter. However, it should be understood that the detailed description and specific examples, while indicating preferred embodiments of the invention, are given by way of illustration only, since various changes and modifications within the spirit and scope of the invention will become apparent to those skilled in the art from this detailed description.